It has been known that, in a wireless communication system such as a portable telephone system, due to an influence from an ambient environment of a mobile terminal (e.g., radio wave interference and reflection of radio waves from a building), an area to which a wireless communication service cannot be provided (e.g., a malfunction area) occurs within a communication area (e.g., a cell or a sector) of each wireless base station. In urban regions or the like, a newly constructed building could change the ambient environment of a mobile terminal, and, as a result, in some case, a wireless communication service is not provided to an area to which the wireless communication service was able to be provided before the building was constructed. Accordingly, in terms of automation of system configuration management, performance optimization, and fault handling based on the SON (Self Optimizing Network) which has been investigated in recent years, it is preferable that a wireless base station recognize without fail the position of an area to which a wireless communication service is not provided.
The following is an exemplary technique used by a wireless base station to recognize the position of an area to which a wireless communication service is not provided. First, the position of an area to which a wireless communication service is not provided is detected by a mobile terminal. In particular, when, for example, a mobile terminal in a connected state (or connected mode) enters an area to which a wireless communication service is not provided, wireless communication between the wireless base station and the mobile terminal will be severed. In this case, as position information indicating the position of the area to which the wireless communication service is not provided, the position information indicating the position of the mobile terminal at the time of severing the wireless communication (e.g., position information indicating, for example, latitude or longitude) is obtained by the mobile terminal using, for example, GPS or the like. Meanwhile, when, for example, a mobile terminal in a standby state (or idle mode) enters an area to which a wireless communication service is not provided, the received power from the wireless base station observed on the mobile terminal side will decrease to a predetermined threshold or lower. In this case, as position information indicating the position of the area to which the wireless communication service is not provided, the position information indicating the position of the mobile terminal at the time of decreasing of the received power to the predetermined threshold or lower is obtained by the mobile terminal using, for example, GPS or the like. As a result, the position of the area to which the wireless communication service is not provided is identified on the mobile terminal side. Next, the mobile terminal comes out of the area to which the wireless communication service is not provided and then establishes a communication channel to the wireless base station using a random access procedure (RACH: Random Access Channel). After the communication channel is established via the random access procedure, the mobile terminal establishes a communication channel to a location service node (E-SMLC: Evolved Serving Mobile Location Center) ordered higher than a plurality of wireless base stations, and reports to the location service node the obtained position information indicating the position of the area to which the wireless communication service is not provided. After this, the location service node reports the position information reported from the mobile terminal to a corresponding wireless base station. As a result, the wireless base station may recognize the position of the area to which the wireless communication service is not provided.
[Patent Document]
    Patent Document 1: Japanese Laid-open Patent Publication No. 2002-271833[Non Patent Document]    Non Patent Document 1: 3GPP TS36.305 “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Stage 2 functional identification of User Equipment (UE) positioning in E-UTRAN”    Non Patent Document 2: 3GPP TR36.902 version 1.2.0 “Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Self-configuring and self-optimizing network (SON) use cases and solutions”